1. Technical Field
This invention generally relates to chute systems. More particularly, the invention relates to a chute system used for conveying documents. Specifically, the invention relates to a spiral chute comprising a plurality of wedge-like chute segments secured together in stepped relationship to each other and between a vertical post and concentric outer wall, and where each chute segment has an upper wall disposed at a first angle to the post and slopes downwardly toward the outer wall.
2. Background Information
Many buildings include chute systems for moving materials from upper floors to a lower floor for processing or disposal. One such system is a chute designed for garbage disposal. In this type of system, a substantially straight chute tube extends between the upper and lower floors in the building and an access door is provided on each floor. Garbage bags introduced through the access doors essentially free fall through the chute from the upper floor to the lower floor. This can prove problematic in that the bags will reach the bottom traveling at a fairly high rate of speed and many of the bags will burst on impact. Consequently, these chutes are often provided with an angled lower region so that the bags will be slowed down by friction as they approach the bottom of the chute. This type of chute system is practical in instances where the flow of material through the chute is sporadic and where the materials moving down the chute are heavy and could become stuck on the chute if the angle thereof was more gradual.
To address some of these issues, a plurality of spiral chutes have been disclosed in the prior art. For example, U.S. Pat. No. 1,802,089, issued to Pfeiffer discloses a gravity feed chute that comprises a plurality of spiral sections that are welded together and is supported between a plurality of external support rods. The chute has a bottom wall that angles inwardly toward the central axis of rotation of the helix. The chute further includes an outer sidewall that extends upwardly from the bottom wall at a gentle angle. The chute is designed to convey materials from an upper elevation to a lower elevation at a substantially constant rate of speed. The angle between the sidewall and bottom wall causes the conveyed material to ride partially up the side wall and the additional friction caused by this contact slows the material down as it travels along the chute. The bottom walls of the adjacent chute segments are substantially coplanar creating a smooth surface over which the material travels.
There are other instances where utilizing a basically vertical chute is not desirable. This is the case when a chute is used for moving materials that are not enclosed in bags or containers, e.g., loose seed. In this instance, if the chute was a vertical tube, the falling seed would generate a large quantity of dust at the base of the chute. A quantity of the seed might also be crushed or damaged by impacting the base of the chute and having a large volume of material fall thereon. Furthermore, the flow rate of the seed would be difficult to control and the material would likely back up the chute. A potential solution to these problems is provided by the chute disclosed in U.S. Pat. No. 3,976,176. This chute is in the form of a suspended spiral channel that is welded at one end to a central post and has an upturned side wall at the outside edge. The chute terminates a short distance from the bottom of the silo. The pitch of the chute is about thirty inches between flights. The bottom wall of the chute is smooth and this allows the seed to flow easily down the chute but not at a velocity that will cause it to be damaged when it exits the chute. As the silo fills up and the bottom of the chute becomes buried, the side wall is short enough to allow seed to progressively spill over the same.
U.S. Pat. No. 5,083,651 discloses a spiral feed chute for conveying tablets and other fragile materials into containers. One of the problems with moving tablets along a feed chute is that they tend to form long lines of single tablets which get backed up in the chute. This is known as freight-training and may lead to crushing of at least some of the tablets and a slowing or halting of the feed process. This patent discloses a chute designed to reduce the tendency for backing up of the product and which promotes the flow of tablets down the chute. The chute comprises a series of spiral flights that are secured between two spaced apart support rods. The flights are connected to each other in a stepped relationship. Each flight comprises a smooth spiral channel with a short sidewall on the outermost edge of the spiral. Each pair of adjacent flights is secured together in a stepped relationship by a strap attached to the undersides of the two chute flights. Additionally, an offset segment secures the two chutes together in such a manner that a portion of the offset extends into the chute channel and a small gap is created between the two adjacent flights. At each joint region, a length of the sidewall of an upper flight overlaps a length of the sidewall of the lower flight thereby forming an offset region that extends into the channel. The step down at the strap combined with the offset, serves to interrupt the flow pattern of materials moving down the chute and thereby prevents the backing up of the same.
U.S. Pat. No. 5,598,914 issued to Sulzer et al discloses a spiral chute that has a center post and an upstanding side wall. The bottom wall of the chute channel either is substantially horizontal or slopes downwardly and inwardly toward the center post. The sections of the side wall are made from stainless steel and are laterally adjustable to decrease the width of the chute channel. This adjustability allows the operator to control the velocity with which different objects travel down the chute.
Other examples of spiral chutes are found in U.S. Pat. No. 4,726,456 to Hogsett and U.S. Pat. No. 6,851,911 to Lhoest.
Spiral chutes have also been used for the disposal of sensitive documents in settings such as government buildings. In these instances, the documents are bagged and introduced through access doors and onto the spiral chute. The chutes currently in use are manufactured from galvanized metal and have the appearance of a swimming pool slide. They may be as large as six feet in diameter, are generally circular in cross-section and may extend downwardly for several floors in larger government buildings. The bags that are placed on the chute may contain a single sheet of paper or may contain up to ten pounds of paper. In the case of particularly sensitive documentation, the hope is that the bag will travel intact down the chute and into a region for incineration without splitting open. What has been found in practice, however, is that the bags do one of two things. Firstly, they slide into the central region of the chute proximate the central post and then simply free fall to the basement where they burst open, spilling the sensitive documentation. Secondly, they do not slide into the central region on the chute and remain on the face thereof, but the bags tend to become stuck somewhere along the length of the chute. This necessitates that every few months a person be sent down the chute to clear any stuck bags and to wax the surface of the chute so that the bags of paper will slide all the way down to the bottom.
There is therefore a need in the art for an improved chute system for conveying articles, particularly documents in closed containers, from an upper elevation to a lower elevation of a building, and without the container breaking open upon reaching the lower elevation.